class Container{
  static of(value){
    return new Container(value);
  }
  constructor(value) {
    this._value = value;
  }
  map(fn){
    return Container.of(fn(this._value));
  }
}

class Maybe {
  static of(x){
    return new Maybe(x);
  }
  isNothing(){
    return this._value === null || this._value === undefined;
  }
  constructor(x) {
    this._value = x;
  }
  map(fn){
    return this.isNothing()?this:Maybe.of(fn(this._value));
  }
}
module.exports = {Maybe, Container};